Permanent magnets have been widely used in proximity switch applications. Sensing actions have generally been accomplished by bringing the magnet sufficiently close to a sensor, for example, a reed switch, to cause it to actuate. The accuracy of position sensing is generally poor as position sensing is strongly dependent on the sensitivity of the reed switch and on the field strength of the magnet, which varies over temperature and initial magnetization. Furthermore, certain applications require careful balancing of the flux fields of multiple magnets to achieve their results.
Night vision goggles (NVG) are commonly used by military personnel for conducting operations in low light or night conditions. The NVG used by the military typically include image intensifier tubes and associated viewable images. Assemblies for mounting NVG to a helmet are well-known in the art. These mounting assemblies allow a user's hands to remain free while viewing a scene through the NVG. Prior mounting assemblies typically include one or more of the following features: positional adjustment of the NVG between an in-use and a flip-up stowage position, tilt angle adjustment of the NVG relative to a user's eyes, focal adjustment of the location of the NVG relative to the user's eyes, and an automatic shutdown of the NVG when the NVG are not in the in-use position.
There is a need to have a reliable and effective automatic shutdown of the NVG when the NVG are not in use. An automatic shutdown allows the user to simply move the NVG out of the user's line of site and allow the user to rely on the NVG to turn off automatically, eliminating the need for a user to activate a switch to turn off the NVG. Many options have been considered to achieve automatic shutdown. Sliding contacts have not been practical because of the severe environmental requirements. Previous proximity switch techniques have also not been satisfactory due to limited space and lack of well defined switch points. Furthermore, standard proximity detector approaches require multiple switches and magnets to logically combine the results of different sensor positions.
The use of a system capable of being environmentally sealed, such as reed switches, provides excellent environmental immunity. There are known methods for automatic shutdown using a magnet module in a cavity, such as allowing a magnet to rotate within a cavity as the user moves the NVG from an in-use position to a flip-up position. However, automatic shutdown may be mistakenly triggered while the user is performing certain combat maneuvers such as rolling over. Since a user's “night vision” and safety may be affected during a critical moment of combat by the mistaken shutdown of the NVG, there is a need for a switch to be coupled to NVG that would reduce or eliminate the possibility of the NVG being accidentally turned off.
Moreover, when the NVG are flipped up, the user has a tendency to forget about their presence. The NVG may protrude beyond the user's helmet and be damaged if the user inadvertently bumps into the surrounding environment, such as the roof inside a vehicle. It is desired for the helmet mount to have a quick stowage feature that allows the night vision goggles to move out of the line of sight, but still within the peripheral vision range to serve as a constant reminder of the presence and location of the NVG. Therefore, it is desired that the switch be able to turn off in both the quick stowage and flip-up stowage positions.
Prior NVG designs are adapted to allow a user to use both eyes for viewing. The NVG is placed directly in front of both eyes and displays an image to both eyes. When a user operates the NVG during low light conditions, a bright light may essentially blind the user through over-exposure of light, disorienting the user for a period of time until the eyes readjust. To limit this problem, it is desired to use a monocular night vision goggle that will provide information to only one eye. The user simultaneously sees an unobstructed view through one eye and an enhanced image in the other. It is desired that the user can locate the night vision goggle in front of either eye, based upon preference or need. Therefore, it is desired that a single helmet mount be used for either eye, eliminating the need for a right eye helmet mount and a left eye helmet mount. Furthermore, it is desired that one switch be used for the helmet mount for both the right eye and left eye.
Thus, there is a need for an improved switch that operates reliably during movement of the NVG from an in-use position to a quick stowage or flip-up stowage position. Furthermore, there is a need for an improved switch to operate when the NVG is in either the right eye position or the left eye position.